The field of art to which this invention pertains is the catalytic dehydrogenation of a dehydrogenatable hydrocarbon to produce an olefinic or aromatic hydrocarbon. The preferred use of the subject method is in the dehydrogenation of alkylaromatic hydrocarbons such as the conversion of ethylbenzene to styrene. The invention is specifically related to an integrated isothermal dehydrogenation zone and an adiabatic dehydrogenation zone wherein the effluent from the isothermal zone is heated in a selective oxidation zone and the concentration of hydrogen is reduced prior to being introduced into the adiabatic dehydrogenation zone.